///69. x 的平方根
///https://leetcode.cn/problems/sqrtx/description/

class Solution {
public:
    int mySqrt(int x) {
        if(x<1)
            return 0;
        int left=1;
        int right=x;
        while(left<right)
        {
            long long mid = left+(right-left+1)/2;
            if(mid*mid<=x)
                left = mid;
            else
                right = mid-1;
        }
        return left;
    }
};